Effects of feed iodine concentrations and milk processing on iodine concentrations of cows' milk and dairy products, and potential impact on iodine intake in Swiss adults

Dairy product and dairy iodine intake among pregnant women in 2 provinces of China: A cross-sectional study

Dairy products, a good source of iodine, have been shown to influence the iodine level of pregnant women. This study aimed to investigate the dairy iodine content, the dairy products, and dairy iodine intake of Chinese pregnant women, and related factors. A cross-sectional study included 1,013 pregnant women in Liaoning and Yunnan provinces, China. The eligible participants completed the intake records for 30 consecutive days to collect characteristics and dairy consumption. Dairy iodine intake was calculated, and the related factors were explored using the Mann-Whitney, Kruskal-Wallis H, and Jonckheere-Terpstra trend tests. An analysis compared dairy iodine intake in pregnant women to the dietary reference intakes of iodine. The iodine content of pasteurized milk (26.3 μg/100 g vs. 14.7 μg/100 g, Z = -2.335) and yogurt (21.5 μg/100 g vs. 12.6 μg/100 g, Z = -2.668) was significantly higher in Liaoning than in Yunnan province. The average dairy intake of pregnant women was 147.4 g/d, and dairy iodine intake was 31.9 μg/d. There were significant differences in dairy iodine intake by age group, province, urban or rural area, ethnicity, and education levels. The median dairy iodine intake in this study only met 12.9% to 23.4% of the estimated average requirement and 9.0% to 16.3% of the recommended nutrient intake (RNI) of local pregnant women in the 2 provinces, respectively. Consuming 500 g of dairy products provides ∼92.5 to 121.0 μg of iodine. Combined with typical iodine intake from iodized salt and other foods, this would help pregnant women meet 105% to 117% of the RNI for iodine. In conclusion, pregnant women with low levels of education, in rural areas, or from the Lahu ethnic group have a lower intake of dairy products and dairy iodine. Approximately 500 g of dairy products plus 5 g of iodized salt and other foods per day will ensure adequate iodine intake for pregnant women in areas with low water iodine.

Variation in milk‑iodine concentration around the world: a systematic review and meta-analysis of the difference between season and dairy-production system

Iodine is essential for thyroid hormone production. Milk and dairy products are important sources of iodine in many countries. We aimed to review systematically the variation in milk‑iodine concentration between countries, seasons and farming practice. We searched online food composition tables and published literature for data since 2006. Milk‑iodine concentration was available for 34 countries (from 66 sources) and ranged from 5.5 to 49.9 μg/100 g (median 17.3 μg/100 g). Meta-analyses identified that iodine concentration is significantly higher in: (i) winter than summer milk (mean difference 5.97 μg/100 g; p = 0.001), and (ii) in conventional than in organic milk (mean difference 6.00 μg/100 g; p < 0.0001). Sub-group analysis showed that the difference between organic and conventional milk was only significant in summer (p = 0.0003). The seasonal variation in milk‑iodine concentration may affect iodine intake and status so should be considered in dietary surveys, and when assessing population iodine status.

Salt Reduction and Iodine Fortification Policies Are Compatible: Perspectives for Public Health Advocacy

Cardiovascular diseases account for almost 18 million deaths annually, the most of all non-communicable diseases. The reduction of dietary salt consumption is a modifiable risk factor. The WHO recommends a daily sodium intake of <2000 mg but average consumption exceeds this in many countries globally. Strategies proposed to aid effective salt reduction policy include product reformulation, front of pack labelling, behavioural change campaigns and establishing a low-sodium-supportive environment. Yet, salt for household and processed food use is, in countries wholly or partially adopting a universal salt iodisation policy, the principal vehicle for population-wide iodine fortification. With salt reduction policies in place, there is concern that iodine deficiency disorders may re-emerge. Recognising the urgency to tackle the rising prevalence of NCDs yet not risk the re-emergence and detrimental effect of inadequate iodine intakes, this review lays out the feasibility of integrating both salt reduction and salt iodine fortification strategies. Reducing the burden of health risks associated with an excessive sodium intake or inadequate iodine through population-tailored, cost-effective strategies involving salt is both feasible and achievable, and represents an opportunity to improve outcomes in public health.

Contribution of plant-based dairy and fish alternatives to iodine nutrition in the Swiss diet: a Swiss Market Survey

PURPOSE

With dairy products and fish being major sources of iodine in Switzerland, the growing popularity of plant-based alternatives may impact iodine nutrition. This study aimed to assess the iodine content in plant-based dairy and fish alternatives available in the Swiss market and compare them with conventional products.

METHODS

In 2022, a market survey was conducted in Zurich, Switzerland, to identify the plant-based dairy and fish alternatives available and assess their iodine content. To evaluate the impact of plant-based alternatives on iodine consumption in Switzerland, we modeled dietary scenarios by substituting the intake of dairy and fish items with plant-based alternatives. In addition, we investigated fortification with calcium, vitamins B2, B12, and D.

RESULTS

Out of 477 identified products, only four milk-alternative products were iodine fortified (median iodine concentration: 22.5 μg/100 ml). The median iodine concentration in unfortified plant-based alternatives was negligible compared to conventional dairy and fish products (milk: 0.21 vs 9.5 μg/100 ml; yogurt 0.36 vs 6.1 μg/100 g; cheese: 0.10 vs 20 μg/100 g; fish 0.50 vs 44 μg/100 g). Three portions of dairy per day as recommended by the Swiss Food Pyramid provide 25% of the RDA for iodine (150 μg/day), whereas substituting those with unfortified alternatives provides only 0.7% of the RDA.

CONCLUSION

Only four out of 477 plant-based alternative products are iodine fortified in the Swiss market. Thus, the risk for consumers to miss out on the ca. 25% of the RDA for iodine by consuming plant-based alternatives is high, placing them at a risk for inadequate iodine intake.

Children's Iodine Intake from Dairy Products and Related Factors: A Cross-Sectional Study in Two Provinces of China

Dairy products are a significant source of iodine, and their contribution to iodine intake must be evaluated regularly. However, there is a lack of data on iodine intake from dairy products in China. Through a cross-sectional study, we determined the iodine content of dairy products in the Chinese diet and estimated iodine intake among Chinese children. Intake records for 30 consecutive days were used to investigate the consumption of dairy products by 2009 children from Yunnan and Liaoning Provinces. The iodine contents of 266 dairy products with high intake frequency were determined using inductively coupled plasma-mass spectrometry (ICP-MS). We then calculated the iodine intake and contribution of dairy products and explored the related factors of dairy iodine intake through a generalized linear mixed model. Ultra-high-temperature (UHT) sterilized milk accounted for 78.7% of the total dairy products, with an iodine content of 23.0 μg/100 g. The dairy product intake rate of children in China was 83.6%, with an average daily intake of 143.1 g. The median iodine intake from milk and dairy was 26.8 μg/d, 41.5% of the estimated average recommendation (EAR) for younger children and 31.8% of the EAR for older children. The daily milk iodine intake of children in Yunnan Province was 9.448 μg/day lower than that of children in Liaoning Province (p < 0.001), and the daily iodine intake of children in rural areas was 17.958 μg/day lower than that of children in urban areas (p < 0.001). Chinese dairy products were rich in iodine, and the content of iodine was intermediate to that reported in Europe and the USA. However, children's daily intake of milk iodine was lower than that of children in other developed countries due to the lower daily intake of dairy products, especially those in rural areas.

Combined Supplementation of Two Selenium Forms (Organic and Inorganic) and Iodine in Dairy Cows' Diet to Obtain Enriched Milk, Cheese, and Yogurt

This study evaluated the effects of dietary supplementation in dairy cows with two Se forms (organic and inorganic) and I at the maximum levels permitted in the European Union, with the aim to obtain naturally enriched milk and derived products. A total of 20 Holstein Friesian cows in lactation were fed 2 diets for 64 days: a control diet with a supply of 0.57 mg of inorganic Se and 0.57 mg of I per kg of ration in dry matter (DM), and an experimental diet (SeI) with a supply of 0.34 mg of inorganic Se, 0.23 mg of organic Se, and 5.68 mg of I per kg of ration in DM. The SeI diet did not modify the performance or, in general, the metabolic profile of cows. Se and I levels in milk were affected by diet type and time of measurement (p < 0.01). Thus, a marked increase of both microminerals was evident between the beginning and the end of the test, when the SeI diet was administered. For Se, this increase ranged from 1.95 to 3.29 μg/100 g of milk; and for I, from 19.69 to 110.06 μg/100 g of milk. The SeI diet increased (p < 0.01) the Se and I content in the cheese, reaching levels of 16.4 μg/100 g for Se and 269.7 μg/100 g for I. An increase in I was observed in yogurt from the SeI diet (p < 0.001). The supplementation of two forms of Se and I in the cows' ration, at the levels evaluated, produced milk and dairy products enriched in these microelements without altering their quality parameters. However, a responsible intake of these products is necessary to avoid risks of deficiencies or excesses that could negatively affect the health of consumers.

Large Iodine Variability in Retail Cows' Milk in the U.S.: A Follow-Up Study among Different Retail Outlets

In a previous study, large variability in iodine content was found among samples of store brand retail milk at a single time point in a sampling taken from 24 nationwide U.S. locations for the USDA FoodData Central database, but the sampling plan was not designed to detect differences among locations. This follow-up study was carried out to evaluate iodine levels in retail milk across the U.S. over time. Milk samples (2% fat) were collected bimonthly in fourteen locations for one year and analyzed in duplicate. Control materials were used to support accuracy of results and ensure precision across analytical batches. The overall mean and standard error (SE) for iodine concentration were 82.5 (7.0) µg/240 mL serving, which was comparable to the previous national mean [85.0 (5.5) µg/240 mL]. A similar wide range among individual samples was detected (27.9-282 µg/240 mL). For some locations, the mean iodine concentration differed significantly from others, and differed from the national average by amounts ranging from -47 µg to +37 µg per serving. The between-sample range within location was large for some (up to 229 µg/serving) and minimal for others (as little as 13.2 µg/serving). These findings suggest iodine intake from some retail milk supplies could be over- or underestimated relative to the national average, even if the national average is suitable for population-wide intake estimates.

Iodine in plant-based dairy products is not sufficient in the UK: A market survey

BACKGROUND

Following a well-balanced diet ensures that a person gets all the essential elements for health sustenance. However, in the United Kingdom an increasing proportion of people are transiting to become vegans who exclude animal-based products in their diets. Consequently, people may have a deficit of essential elements such as iodine which is not present in most plant-based meals, additionally iodide fortified table salt is not commonly used in the UK. Without iodine people consuming a vegan diet risk developing iodine deficiency and diseases like goiter.

METHODS

The objective of this study is to determine the difference in iodine content and iodine speciation between plant-based and dairy products. More than 100 market samples of plant-based and dairy milk products were collected in Scotland, UK.

RESULTS

Iodine concentrations in dairy milk is ten times higher compared to plant-based milks. Similar differences were also apparent for butter, yogurt and cheese. A total of 20% of plant-based milk products were fortified with iodine, however these products had lower iodine concentrations compare to the equivalent dairy products. In this study we calculated that people with average diet have an iodine intake of 226 + /- 103 μg day^-1 from dairy products which satisfies the WHO recommended intake of adults and 90% of the recommend intake for pregnant and breast-feeding women. A diet from substituted dairy products gives only 21.8 µg day^-1 for the respective WHO guideline intake values, which accounts only 15% of the iodine intake for adults and 9% for pregnant and lactating women. Iodine fortified diet could increase the iodine intake to 55% or 33% of the WHO recommended daily intake respectively.

CONCLUSION

Plant-based dairy consumers are encouraged to use iodine fortified dairy products or use of iodized salt in the UK for home cooking, otherwise there are at risk to get iodine deficient.

Invited review: Iodine level in dairy products-A feed-to-fork overview

The theme of iodine in the dairy sector is of particular interest due to the involvement and the interconnection of several stakeholders along the dairy food chain. Iodine plays a fundamental role in animal nutrition and physiology, and in cattle it is an essential micronutrient during lactation and for fetal development and the calf's growth. Its correct use in food supplementation is crucial to guarantee the animal's recommended daily requirement to avoid excess intake and long-term toxicity. Milk iodine is fundamental for public health, being one of the major sources of iodine in Mediterranean and Western diets. Public authorities and the scientific community have made great efforts to address how and to what extent different drivers may affect milk iodine concentration. The scientific literature concurs that the amount of iodine administered through animal feed and mineral supplements is the most important factor affecting its concentration in milk of most common dairy species. Additionally, farming practices related to milking (e.g., use of iodized teat sanitizers), herd management (e.g., pasture vs. confinement), and other environmental factors (e.g., seasonality) have been identified as sources of variation of milk iodine concentration. Overall, the aim of this review is to provide a multilevel overview on the mechanisms that contribute to the iodine concentration of milk and dairy products.

Optimizing Growth: The Case for Iodine

Iodine is an essential micronutrient and component of thyroid hormone. An adequate dietary iodine intake is critical to maintain and promote normal growth and development, especially during vulnerable life stages such as pregnancy and early infancy. The role of iodine in cognitive development is supported by numerous interventional and observational studies, and when iodine intake is too low, somatic growth is also impaired. This can be clearly seen in cases of untreated congenital hypothyroidism related to severe iodine deficiency, which is characterized, in part, by a short stature. Nevertheless, the impact of a less severe iodine deficiency on growth, whether in utero or postnatal, is unclear. Robust studies examining the relationship between iodine and growth are rarely feasible, including the aspect of examining the effect of a single micronutrient on a process that is reliant on multiple nutrients for optimal success. Conversely, excessive iodine intake can affect thyroid function and the secretion of optimal thyroid hormone levels; however, whether this affects growth has not been examined. This narrative review outlines the mechanisms by which iodine contributes to the growth process from conception onwards, supported by evidence from human studies. It emphasizes the need for adequate iodine public health policies and their robust monitoring and surveillance, to ensure coverage for all population groups, particularly those at life stages vulnerable for growth. Finally, it summarizes the other micronutrients important to consider alongside iodine when seeking to assess the impact of iodine on somatic growth.

ESPEN micronutrient guideline

BACKGROUND

Trace elements and vitamins, named together micronutrients (MNs), are essential for human metabolism. Recent research has shown the importance of MNs in common pathologies, with significant deficiencies impacting the outcome.

OBJECTIVE

This guideline aims to provide information for daily clinical nutrition practice regarding assessment of MN status, monitoring, and prescription. It proposes a consensus terminology, since many words are used imprecisely, resulting in confusion. This is particularly true for the words "deficiency", "repletion", "complement", and "supplement".

METHODS

The expert group attempted to apply the 2015 standard operating procedures (SOP) for ESPEN which focuses on disease. However, this approach could not be applied due to the multiple diseases requiring clinical nutrition resulting in one text for each MN, rather than for diseases. An extensive search of the literature was conducted in the databases Medline, PubMed, Cochrane, Google Scholar, and CINAHL. The search focused on physiological data, historical evidence (published before PubMed release in 1996), and observational and/or randomized trials. For each MN, the main functions, optimal analytical methods, impact of inflammation, potential toxicity, and provision during enteral or parenteral nutrition were addressed. The SOP wording was applied for strength of recommendations.

RESULTS

There was a limited number of interventional trials, preventing meta-analysis and leading to a low level of evidence. The recommendations underwent a consensus process, which resulted in a percentage of agreement (%): strong consensus required of >90% of votes. Altogether the guideline proposes sets of recommendations for 26 MNs, resulting in 170 single recommendations. Critical MNs were identified with deficiencies being present in numerous acute and chronic diseases. Monitoring and management strategies are proposed.

CONCLUSION

This guideline should enable addressing suboptimal and deficient status of a bundle of MNs in at-risk diseases. In particular, it offers practical advice on MN provision and monitoring during nutritional support.

Changes in organoleptic, microbiological and biochemical properties of kefir with iodine addition during the storage

Iodine is a vital trace element that must be constantly and daily supplied with food to the organism. Currently, the amount of food that can provide the organism with the required amount of iodine is insufficient. The purpose of the study was to investigate changes in organoleptic, microbiological, and biochemical parameters of kefir made with the addition of iodine during its refrigeration storage. It was found that during the storage of samples of kefir with iodine there is a slowdown in the reproduction of lactic acid bacteria, compared with the control sample. In particular, the number of lactic acid bacteria during the first two days of storage increased 1.3 times in the experimental sample and 1.5 times in the control sample of kefir. After 12 days of storage, the number of lactobacilli in the test sample of kefir increased 2.5 times, and in the control 3.2 times, compared with the amount in fresh kefir. Similar patterns were observed in determining the development of yeast. In particular, the reproduction rate of yeast in the control sample of kefir was, on average, 1.3 times faster (8 – 12 days), compared with yeast in the experimental sample. It was also found that during the 12-day storage period at a temperature of +6 °C, the titrated acidity in kefir with iodine increased 1.4 times, and in the control 1.6 times and was 130.5 °T and 154.1 °T, respectively. At such acidity values, the test sample of kefir still met the requirements of the standard, and the control was 24.1 °T higher. In this case, kefir containing iodide had better organoleptic characteristics during 12 days of storage. Produced kefir with the addition of iodine can be considered a functional product to provide the population with sufficient iodine.

Iodine supplementation: is there a need?

PURPOSE OF REVIEW

To review the recent data on iodine deficiency, the impact of iodine deficiency on health outcomes and the need for iodine supplementation in at-risk populations, that is, pregnant and lactating women, infants and young children.

RECENT FINDINGS

The 2019 Iodine Global Network Annual Report highlighted that only 23 countries worldwide (including Finland, Germany, and Norway in Europe) were classified as having insufficient iodine intake in 2019, down from 54 in 2003 and 113 in 1993. Even if severe iodine deficiency during pregnancy has a negative impact on cognitive outcomes later in life, the consequences of mild-to-moderate iodine deficiency on child neurodevelopment are controversial. Two 2017 and 2019 Cochrane Systematic Reviews found no evidence that iodine supplementation in women before, during or after pregnancy improved infant and child cognitive development in areas with mild-to-moderate iodine deficiency. Likewise, a 2019 Cochrane systematic review concluded that there was no evidence of a positive impact of iodine supplementation on morbidity, including cognitive impairment, and mortality in preterm infants.

SUMMARY

There is no scientific evidence to support generalized iodine supplementation in mildly to moderately deficient settings not only in pregnant and lactating women but also in infants, either preterm or term, and in young children.

Iodine status of Turkish pregnant women and their offspring: A national cross-sectional survey

BACKGROUND

This national cross-sectional survey aimed to assess the iodine status in pregnant women and their offspring, and also to demonstrate regional differences by measuring urinary iodine concentration (UIC). For each woman and her newborn a questionnaire was prepared with basic facts as age, parity number or birth weight and additional information regarding thyroid diseases, use of iodized salt in the household, extra iodine supplementation during pregnancy, education level and wage income.

METHODS

The target population represented 1444 pregnant women who gave birth between January 1 st, 2018 and 2019, and their offspring. Iodine deficiency for pregnant women and their offspring were defined as urine iodine level <150 μg/L and <100 μg/L, respectively. Results are given as median (25th-75th percentile).

RESULTS

The median UIC in the group of pregnant woman was 94 (52-153) μg/L. Within the sample of 1444 pregnant women, UIC indicative of mild iodine deficiency (100-149 μg/L) was present in 21 % (n = 306), moderate deficiency (50-99 μg/L) in 30 % (n = 430), and severe deficiency (<50 μg/L) in 23 % (n = 337). This study showed a prevalence of 74 % of iodine deficiency in Turkish pregnant woman. The median UIC in the group of offspring was 96 (41-191) μg/L. Within the new-borns, UIC indicative of mild iodine deficiency (50-99 μg/L) was present in 22 % (n = 323), moderate deficiency (20-49 μg/L) in 15 % (n = 222), and severe deficiency (<20 μg/L) in 13 % (n = 192). This survey showed a prevalence of 51 % of iodine deficiency in Turkish new-borns. Pregnant women with lower socioeconomic and education level, lower access to household iodized salt, lower rates of exposure to povidone-iodine containing skin disinfectant, higher parity and higher iodine deficiency had higher rates of iodine deficiency in their offspring. Regional differences were observed both in mothers and their offspring concerning their iodine status.

CONCLUSIONS

Our findings suggest that iodine deficiency is still an important public health problem in Turkey. More drastic measures should be taken to decrease these important iodine deficiencies, both in pregnant women and in their offspring.

Changing Dietary Habits in Veneto Region over Two Decades: Still a Long Road to Go to Reach an Iodine-Sufficient Status

Background: Fifteen years after a nationwide voluntary iodine prophylaxis program was introduced, the aims of the present study were: (a) to obtain an up-to-date assessment of dietary iodine intake in the Veneto region, Italy; and (b) to assess dietary and socioeconomic factors that might influence iodine status. Methods: Urinary iodine concentration (UIC) was obtained in 747 school students (median age 13 years; range: 11–16 years). Results: The median UIC was 111 μg/L, with 56% of samples ≥ 100 μg/L, but 26% were < 50 μg/L, more frequently females. Iodized salt was used by 82% of the students. The median UIC was higher among users of iodized salt than among non-users, 117.0 ug/L versus 90 ug/L (p = 0.01). The median UIC was higher in regular consumers of cow’s milk than in occasional consumers, 132.0 μg/L versus 96.0 μg/L (p < 0.01). A regular intake of milk and/or the use of iodized salt sufficed to reach an adequate median UIC, although satisfying only with the combined use. A trend towards higher UIC values emerged in regular consumers of cheese and yogurt. Conclusion: Iodine status has improved (median UIC 111.0 μg/L), but it is still not adequate as 26% had a UIC < 50 μg/L in the resident population of the Veneto region. A more widespread use of iodized salt but also milk and milk product consumption may have been one of the key factors in achieving this partial improvement.

Large Variability of Iodine Content in Retail Cow's Milk in the U.S

Iodine intake is of contemporary public health interest. The recommended daily iodine intake is 150 µg for most adults, and milk is an important source of iodine in the U.S. diet. Iodine concentration in cow's milk is affected by diet and iodine supplementation levels, milking sanitation practices, and other factors. Current analytical iodine data in U.S. retail milk are crucial for evaluating population-wide health outcomes related to diet. Samples of whole (3.25% fat), 2%, 1%, and skim (0-0.5% fat) milk were procured from 24 supermarkets across the U.S. using a census-based statistical plan. Iodine was analyzed by inductively coupled plasma mass spectrometry, including certified reference materials and control samples to validate results. No difference in iodine content was found between milkfat levels (F3,69 1.033, p = 0.4). Overall mean (SEM) was 85(5.5) µg/serving (240 mL). However, the 95% prediction interval of 39-185 µg/serving for individual samples indicated high variability among individual samples. Given the recommended 150 µg iodine per day for most adults along with the study mean, one milk serving can provide approximately 57% of daily intake. Researchers, health care professionals, and consumers should be aware of iodine variability in milk, while additional research is needed to investigate the impact of iodine variability factors.